The lawsuit — announced on Monday — is the fourth lawsuit filed against the Delta Plan over the past month.

The plaintiffs, including AquAlliance and Friends of the River, say the plan would harm fishing and farming and put several endangered species at increased risk of extinction.

The Delta Plan aims to provide a more reliable water supply for cities and farms, and protect and restore the delta ecosystem. The $14 billion twin-tunnel project will be incorporated into the plan if the tunnels are approved and permitted.

Water contractors, who have also filed suits against the plan, say it would result in substantial reductions in water deliveries.